Non-invasive imaging is one of the major factors that propelled medical science and treatment over the past decades. By assessing the characteristics of human tissue, imaging is often used in clinical practice for oncologic diagnosis and treatment guidance. A key goal of imaging is personalized medicine, were the treatment is tailored towards the specific characteristics of the patient. For personalized medicine, recent developments in the fields of genomics and proteomics have enabled the molecular characterization of tissue, such as neoplasms (i.e. tumors). However, as tumors are spatially and temporally heterogeneous, these techniques are limited, as they require biopsies or invasive surgeries to extract part of the tissue under study. Therefore, imaging can be of large importance as imaging can capture intra-tumoral heterogeneity, is already performed in routine practice, is non-invasive, and can be acquired during time.
Probably the most widespread imaging modality is computed tomography (CT), assessing the density of the tissue. Moreover, also positron emission tomography (PET) is a common imaging method applied in diagnosis and treatment of tumors. Positron emission tomography is based on the use of a radioactive tracer, i.e. a positron-emitter. For example a patient is given an injection of a small amount of a radioactively labelled glucose. Cancer cells capture more glucose than most of other tissues in the body, thereby enabling detection and imaging of the tumor. To enable treatment by means of personalized medication, it is highly desired to obtain information on treatment effectiveness of a followed treatment plan. As may be appreciated, early detection of an ineffective treatment enables a physician to review and modify the personalized medication at an early stage. The sooner an effective treatment is identified, the higher will be the chance on success of the treatment.